The present invention relates to a testing system usable for testing the quality and for measuring various characteristics of a variety of semiconductor devices, such as monolithic and hybrid semiconductor integrated circuits or module circuits.
Recent technical trends related to the design of semiconductor integrated circuits involve an increase in the number of functions performed by an integrated circuit. For example, there is a semiconductor integrated circuit (referred to as simply "IC" hereinafter) that is arranged so as to be usable as a radio receiver, a television receiver and a recording-playback system. On the other hand, with respect to digital functions, there are ICs having various "microcomputer functions". Moreover, there is also an IC that comprises both circuits having an analog function and circuits having a digital function. In such ICs having multiple functions or composite functions, there is inevitably an increase in the number of measuring items (testing items) requiring the measurement of A.C. parameters and D.C. parameters.
Measuring systems for measuring parameters as mentioned above generally have a D.C. parameter measuring portion as a basic component part. FIG. 1 is a block diagram of a testing system considered by us prior to the present invention.
A matrix circuit 1 has its Y axes lines connected to respective external connecting terminals (connection pins) P of an IC 2. Although, if the IC 2 has 28 connection pins, the 28 connection pins P normally are all connected to circuit elements of the IC; however, for convenience of description, only a few circuit elements of the IC are shown. Moreover, the matrix circuit 1 has its X axes lines connected to the measuring sources e.sub.1 to e.sub.6 for measuring various parameters of the IC 2. The measuring sources e.sub.1 to e.sub.6 should be different from each other in voltage level, current level and the like. In addition, the output ends of the Y axes lines are connected to an A/D converter 3 and a measuring discriminator 4. Further, the Y axes lines and the X axes lines can be selectively connected together at their respective cross points by means of reed relays (not shown). Therefore, if the Y.sub.1 and X.sub.1 lines, for example are connected together at their cross point through the corresponding reed relay, a signal e.sub.1 is supplied to the IC 2. Then, the output signals of amplifiers 2a, 2b are supplied to the measuring discriminator 4 via the cross point between lines Y.sub.2 and X.sub.7 and the cross point between lines Y.sub.3 and X.sub.7 through the A/D converter 3. As a result, the qualities of the amplifiers 2a, 2b are tested by the measuring discriminator 4.
The testing mentioned above is a test of the amplifiers 2a, 2b with respect to only the signal source e.sub.1. In practice, it is necessary to carry out a similar testing with respect to the other signal sources e.sub.2 to e.sub.6 according to need. As a consequence, there is a need for a large number of signal sources for testing in the case of inspecting an IC having both analog functions and digital functions. Accordingly, it is also necessary to provide a large number of reed relays corresponding to the matrix cross points associated with the signal sources.
The D.C. parameter measurement is substantially the same as the semiconductor element test and requires only a short measuring time. The A.C. parameter measurement, however, is substantially the same as the mounted circuit test and generally takes a much longer time than the D.C. parameter measurement, since there are included in the test intrinsic time-constants determined by external inductance L, capacitance C, resistance R and the like. Therefore, the A.C. parameter measurement is replaced by the D.C. parameter measurement, and the number of D.C. parameter measuring items increases with any increase in the degree of integration. Accordingly, the essential subject of the testing system is the increase in the measuring speed rather than economy.
Therefore, we have examined technical trends of ICs and testing systems. As a result, it has been made clear that conventional testing systems have the following defects.
(1) Measuring time per connection pin is long: it takes 2 to 3 msecs.
(2) It is necessary to increase the number of reed relays in a matrix circuit in correspondence with the increase in the number of connection pins, resulting in a more complicated circuit configuration.
(3) The reed relay has a low reliability and is also expensive, causing the system to be higher in cost as a whole.
(4) It takes much time to measure all of the test data, since measured results are serially supplied to the measuring discriminator through the A/D converter.